The present invention relates to an illuminating device and, more particularly, to an illuminating device for a projector which improves the efficiency of the use of light by using light normally not focused by a parabolic mirror.
Referring to FIG. 1, a conventional illuminating device used as a light source of a projector for projecting an image onto a screen, includes a lamp 1 which emits light and a parabolic mirror 2 which reflects and converts the light emitted from the lamp 1 into parallel light rays 3. The parallel light rays 3 reflected from the parabolic mirror 2 pass through a liquid crystal display device (not shown) which forms an image according to electrical signals and then is projected onto a screen (not shown).
In such a projector, since light needed to form an image on a screen among the light emitted from the lamp 1 are the parallel rays 3 which are reflected from the parabolic mirror 2, non-reflected light 4 which is not reflected by the parabolic mirror 2 but radiates outside does not contribute to the formation of the image. Thus, the efficiency is lowered due to the loss of light in the conventional illuminating device for a projector which lacks the means for converting the non-reflected light 4 into a parallel beam of light rays.